Electromagnets have been used in variety of work environments, and are particularly useful in environments that require lifting, moving, or transporting large amounts of magnetic materials. For example, electromagnets may be used in shipping ports to move containers from ships in port to flatbed truck trailers for ground transportation. Alternatively, electromagnetic lifts may be employed in scrap yards to move, organize, and load scrap material for recycling or reprocessing.
Electromagnets are typically powered by a electrical power source, which produces a magnetizing current to the coils of the electromagnetic lift. The current induces a strong magnetic field on the face of the electromagnetic device, which can be used to lift and transport metallic or magnetic materials. The current that is input to the electromagnet may be turned on and off through the use of operator-controlled switches. By controlling the switches, an operator can energize the electromagnet to lift and hold an object and de-energize the electromagnet to drop the object.
One such electromagnetic lift system is described in U.S. Pat. No. 5,325,260 (“the '260 patent”) to Repetto. The '260 patent describes a power source and control system for an electromagnetic lift. The electromagnetic lift is powered by a DC-rectified AC power source (e.g., an alternator) coupled to an electromagnet via relay devices. The relay switches can be manually operated to supply energizing current to the electromagnet to lift, transport, and drop objects using electromagnetic lift.
Although the system described in the '260 patent may provide an electromagnetic lift system for transporting objects within a work environment, it may still be inadequate and inefficient. Specifically, the system of the '260 patent only allows the operator to toggle the electromagnet between on and off states (i.e., “lift” and “drop”). Often, material that is initially lifted and held by the electromagnet may loosen during transport, due, for example, to vibration of the boom and/or interaction with other material held by the electromagnet. Consequently, objects that become dislodged may fall from the electromagnet before being transported to their intended destination, which may increase the time required to perform material transfer tasks associated with certain work environments, potentially limiting the overall productivity of the work environment. In addition to any costs associated with lost productivity, material that falls from the boom may be damaged and/or may damage the machine, potentially decreasing work site profitability. Accordingly, in order to minimize inefficiency and damage to a work environment resulting from objects that become dislodged and fall from an electromagnetic lift, a system for limiting the amount of loosely-held material transported by the electromagnet may be required.
The presently disclosed system and method for controlling electromagnetic lift power for material handlers are directed toward overcoming one or more of the problems set forth above.